The conservative Partido Popular was in power from 1996 until 2004 when they were ousted in part because of popular anger against the war in Iraq. During - and even after their time at the helm - a series of undisclosed payments were allegedly made to senior party officials listed in handwritten notes kept by Luis Bárcenas, the party’s former treasurer and his colleague Álvaro Lapuerta, that were revealed in El País newspaper last week.

Questions are now being raised about the possible connections between the lucrative public sector contracts and the Bárcenas payments, which came to light when the former party treasurer submitted details of a secret Swiss bank account to the tax authorities under an amnesty program set up shortly after Rajoy came to power. The account, which was operated by Bárcenas, held as much as €22 million at times.

Mariano Rajoy, the current Spanish prime minister, has been accused of personally receiving €25,200 ($34,100) a year from the slush fund over a period of 11 years starting in 1997 when he served first as minister of public administration and later as deputy prime minister.